What began as a local river crossing in 1935, the Interstate 74 & U.S. 6 bridges (Iowa-Illinois Memorial Bridge) across the Mississippi River between Moline and Davenport are reaching the end of their life span. Though never built to Interstate standards, the 1935-northbound bridge and 1959-built southbound span were added to the Interstate system in 1974. Each suspension bridge carries two lanes without left or right-hand shoulders. The safety issues alone warrant a change, but the bridge design does not allow for any expansion, with a pony truss style siding constructed along east side. Additionally the bridge was already over capacity by 1998, with 74,000 vehicles per day (vpd) crossing a span that can only adequately handle 64,000 vpd.

Picture of the Illinois-Indiana Memorial Bridge from the north banks of the Mississippi River at Bettendorf. A levee system protects the downtown area of Bettendorf from the river. Along the barrier is a walk/bike path, boat ramp, park area, and the Isle of Capri Casino.

Forward to May 23, 2006, the Iowa and Illinois Departments of Transportation held a joint public meeting to select the recommended bridge type for the Interstate 74 replacement. Four designs were considered until the end, the first consisted of a basket handle true arch twin bridge, essentially spans side by side with arches that converge at the top. Second on the list was a modified basket handle tied arch bridge design, with vertical pier and hangers. This configuration is similar in design to what is used for Interstate 280’s crossing of the Mississippi River west of Rock Island, with cross members joining two sets of arches on each span. Design three was similar to the basket handle design but with tied arches. The final design consisted of a cable stayed sing bridge with a semi-fan stay arrangement, essentially a cable-stayed bridge with three support towers. View the designs for yourself here http://projects.ch2m.com/I74Study/Assets/Finalist%20Bridge%20Type%20views_posters.pdf

The Iowa-Illinois Memorial Bridge travels 66 feet above the Mississippi and is 5,148 feet in overall length.

Its name honored the veterans of World War I during its dedication (northbound span) on November 18, 1935. The southbound bridge was built for $8.1 million in 1958, with both open for traffic after a 1959 closure of the original for repairs on January 20, 1960.

After the public meeting held jointly by Iowa and Illinois DOTs, the new bridge was chosen as officials announced the basket handle true arch twin bridge design. The new bridge will accommodate a bike path and observation platform, similar in scope to the Arthur Ravenel Jr. Bridge in Charleston, South Carolina. Additionally each span will carry four overall lanes with full inside and outside shoulders.

Approaching the south tower of Interstate 74 & U.S. 6 east as travelers enter Moline, Illinois. The bridge originally carried just U.S. 6 until the 1974 addition of Interstate 74. Work connecting the Illinois-Iowa Memorial Bridge to new Interstate 74 began in 1971 and was completed on November 26, 1974. Interstate 74 was finished in Quad Cities on December 10, 1975.

Due to the importance of the existing Interstate 74 & U.S. 6 bridge to the daily traffic movements of the Quad Cities, the span will remain open during construction of its replacement. The new span will be built just east of the existing, which works because the present freeway takes a bend in Moline before spanning the Mississippi to Bettendorf and Davenport. Work will also entail building a new south approach and reworking the north approach into the new bridge. That scope of the work does not end there however, as adjacent interchanges will also be reworked in conjunction with a widening to six-lanes of the overall freeway (with several eight lane sections due to new auxiliary lanes). See schematics of the new alignment and ramps changes here http://projects.ch2m.com/I74Study/Assets/2006_05_23_Meeting.pdf.

A platform joins both spans of the Interstate 74 & U.S. 6 Bridge over the south banks of the Mississippi River. The platform used to support toll collection facilities (15 cents per direction), which were removed on January 1, 1970.

As time passes, costs of the new span continue to escalate. Originally estimated to cost $600-million in 2002, prices increased to $650 million in 2006 and now have increased to $791 million. With all of the push backs during the study phase, filing of an Environmental Impact Statement, finalizing a bridge alternative, the construction timetable shifted from a potential completion date of 2011 early on to a construction start date no sooner than 2012. If you factor in the overall corridor expansion project from 53rd Street in Davenport to Avenue of the Cities in Moline, the completion day may await until December 2022.

For an in depth look at route numbering changes and a construction time line of the Quad Cities Interstate system and proposed Interstate renumbering, please see Jason Hancock’s Highways of Davenport and Bettendorf.

Sources:

  • “Bridges to the Future.” River Cities’ Reader, August 13, 2002.
  • i-74corridorstudy.org – Iowa Department of Transportation / Illinois Department of Transportation.
  • “New estimate puts cost of I-74 bridge at $791 million.” QC Times, February 26, 2008.
  • “New I-74 Bridge Plan Chosen.” WBHF 4, Quad Cities, August 30, 2006.
  • I-74 Iowa-Illinois Memorial Bridge, John Weeks.
  • Mississippi Bridge Timeline (QCQ&A), http://qconline.com/progress2005/stories.cgi?section=pr051&prcss=display&id=228840 Quad Cities Online.